Various types of photoacoustic sensors are known to detect gases. These include, Fritz et al., US Patent Application No. 2009/0320561, published Dec. 31, 2009 and entitled “Photoacoustic Cell”; Fritz et al., US Patent Application No. 2010/0027012, published Feb. 4, 2010 and entitled, “Photoacoustic Spectroscopy System”; Fritz et al., US Patent Application No. 2010/0045998, published Feb. 25, 2010 and entitled “Photoacoustic Sensor”; and Tobias, US Patent Application No. 2010/0147051, published Jun. 17, 2010 and entitled, “Apparatus and Method for Using the Speed of Sound in Photoacoustic Gas Sensor Measurements. The above noted published applications have been assigned to the assignee hereof, and are incorporated herein by reference.
Some known types of photoacoustic sensors incorporate resonant sensors. Others include gas valves. Members of another class of photoacoustic sensors incorporate diffusion membranes.
Diffusion membranes in photoacoustic sensors provide controlled ambient gas permeation into a sensing region. They also contribute to photoacoustic pressure confinement and bound a working volume of the photoacoustic chamber or sensing region.
In known sensors or detectors, this membrane is is attached with a layer of adhesive material. The adhesive material exhibits inherent problems which can impact functional performance of the membrane thus produce a strong impact on the functional performance of the photoacoustic sensor. These problems include: strong susceptibility to delaminate due to ambient conditions (temperature, humidity), and susceptibility to delaminate due to dimensional changes of a substrate as a function of ambient temperature variations (expansion and contraction). Membrane degradation, as described above, results in photoacoustic pressure variance or loss of the photoacoustic signal. Proper functioning of the diffusion membrane for these types of photoacoustic sensors is important for successful construction and functioning of the photoacoustic sensor.